Method for encasing magnetic cores



Au 10, 1965 BRANDON, JR., ETAL 3,199,177

METHOD FOR ENCASING MAGNETIC CORES Original Filed May 24, 1955 INVENTORS JAMES CAMPBELL BRANDON, JR. THEODORE HENRY FRA A/K, JR ROBERT HOWARD RAH/SEE skawlbax (M ATTORNEY S United States Patent METHGD FGR ENCASEENG MAGNETHC CURE?) .l'amcs Campbell Brandon, Jan, and Theodore Henry Franir, .ha, Butler, and Robert Howard ltahiser, Evans City, ll m, assignors to Magnetics, lino, Butler, Pa, a corporation of Pennsylvania @riginal application May 24, 1.955, Ser. No. 510,635, new Patent No. 3,ll8,d55, dated .lan. 23;, W52. Divided and this application Lian. 1%, HM, Ser. No. 17$,dtl4l This application is a division of Patent No. 3,018,455, issued January 23, 1962.

This invenion relates to magnetic core devices and particularly to encasements for magnetic cores and methods for cushioning such a core within an encasement.

The phrase magnetic cores as used herein is intended to include not only toroidally shaped endless or annular cores but also cores having hollow square, rectangular or other configurations in plan view with or without an air gap in their circumference. Magnetic cores are well known in the art and are particularly useful with magnetic amplifiers, saturable reactors, saturable transformers, magnetic relays, and the like. In the prior art such cores have been fully encased in a thermosetting plastic material or in nylon boxes. It has been found that the strain produced in the core by winding copper wire windings around the encasement undesirably changes the magnetic characteristics of the magnetic core. This frequently is true even though a cushioning material is disposed between the core and the encasement, because plastic and nylon boxes do not have sulficient structural strength to prevent deflection and distortion of the magnetic core when mechanical stresses are imposed on its encasement.

The present invention obviates the above-mentioned problems by providing a metallic container having a structural strength much greater than the prior art plastic and nylon boxes. A core cannot be entirely surrounded by continuous metallic material, however, since a full metallic encasement would allow eddy currents to be set up Within the metallic encasement and thereby reduce th effective inductance of the core.

One phase of the invention provides a full encasement comprising a metallic, non-magnetic container disposed partially around the magnetic core, the remainder of th encasement being closure means made of non-metallic material having strength characteristics approximating the strength characteristics of the metallic container. Therefore, any eddy currents tending to be induced in the metal container will be prevented and the full flux created will be permitted to link the winding placed about the core.

Another phase of this invention provides for non-magnetic, metallic closure means secured against the metallic container but electrically insulated therefrom. I Another phase of this invention in conjunction with either of the preceding phases, is the provision of an encasement which will withstand temperatures up to approximately 500" F. This is an important feature since modern day magnetic core devices are utilized in extremely compact equipment such that for aircraft.

Still another phase of this invention is the provision of a novel nethod of cushioning the magnetic core Within the encasement. Small discrete quantities of silicone rubber are distributed within the container for the magnetic core to rest against. The core is then inserted and other small discrete quantities of silicone rubber are spaced around the exposed portion of the core. The closure means is then placed upon shoulders provided in the metallic container and the open end portions of the container are folded over the closure means. The core then is fully enclosed and cushioned. The rubber cushion prevents vibration and shock from being transmitted into the 'ice magnetic material of the core in such a fashion as to adversely affect magnetic properties.

Another phase of this invention is the sealing of th encasement to allow subsequent vacuum impregnation. The folding over of the end portions presses the closure means tightly against the shoulders of the container and thereby provides a seal. To insure even a more perfect seal, sealing compounds may be applied before folding over the end portions.

Yet another phase of this invention is to prevent shorting of windings placed about the encasement to the met-allic container. In this respect, a silicone varnish is applied at least to a portion of the outside of the metallic container and, preferably but not necessarily, to the eX- posed portions of the closure means. If silicone rubber is used for cushioning, the rubber and varnish may be cured simultaneously.

In the prior art, the cushioning material frequently utilized is grease or oil packed fully between the core and non-magnetic box. A cushioning material of this type may be utilized with this invention; however, after insertion of such a grease or oil it has frequently been found difficult to remove the seemingly inevitable excess thereof from the shoulders or ledge upon which the closure or lid rests and defective sealing has resulted. The above-mentioned silicone rubber cushioning completely obviates this diflicultyl A primary object of this invention is to provide an encasement for a magnetic core so that winding placed about the encasement cannot deflect or distort the core and thereby change the magnetic characteristics of the core.

Another object, in conjunction wit-h the above object, is the provision of an encasement made partially of nonmagnetic metal, the remainder of the encasement being at least partially an insulating material to prevent induced eddy currents.

Another object of the invention in conjunction with the preceding object, is to construct said remainder wholly of non-metallic materials.

Still another object of the invention is to provide for a magnetic core an encasement comprising two parts both of non-magnetic, metallic materials insulated from each other when assembled.

Still another object of the invention is to provide for a magnetic core an encasement which will withstand temperatures up to approximately 500 F.

Another object of the invention is to provide for a magnetic core a partially metallic, sealed encasement which will withstand vacuum impregnation of the windings on the encasement.

A further object of this invention is to provide for a magnetic core a partially metallic encasement having at least a predetermined amount of the metal casing covercd with insulation so that the windings placed thereabout may not be damaged during assembly or shorted to the metal casing.

Another object of the invention is to provide material between a magnetic core and encasement for cushioning the core without surrounding it completely.

Another object of the invention in conjunction with the preceding object, is to make the cushioning material of silicone rubber placed in small discrete quantities at least on two sides of the core.

A further object of the invention in conjunction with the preceding object, is to make the cushioning material of silicone rubber placed in small discrete quantities at least on two sides of the core.

A further object of the invention in conjunction with the preceding object, is to place the silicone rubber in predetermined places on all four sides of the core.

Further objects and the entire scope of the invention arcane/7 3 will become further apparent from the following detailed description of the exemplary embodiments of the various phases of t is invention.

The exemplary embodiment according to the invention may be best understood with reference to the accompanying drawing wherein:

FIGURE 1 is a perspective view of a magnetic tape wound core encased in accordance with this invention. Parts are broken away to illustrate details;

FIGURE 2 is a cross-sectional view taken approximately along the line 2 2 of FIGURE 1;

FIGURES 3 and 4 illustrate one embodiment for cushioning a magnetic core within an encasement; FIGURE 4 being a cross-sectional view of the container of URE 3 with parts added; and

FIGURES 5 and 6 illustrate another embod' cushioning of a magnetic core with an encasemc. URE 6 being a cross-sectional view of the container of FIGURE 5 with parts added.

In reference now to the drawings, there is shown in FEGURES 1 and 2 a magnetic core device having a magnetic core 11? surrounded by an inert cushioning material 13, such as silicone grease or oil, all of which is partially enclosed in a non-magnetic, toroidal metallic container 12, which is U-shaped in radial section. At the open end of the container 12 the inner and outer ails thereof are formed with interior circumferential ledges or shoulders 14 against which is set a non-metallic closure means such as the annular lid 16. The end portions of the inner and outer walls extending beyond the lid 15 have been folded over the latter (for example, by crimping or spinning) to hold it in place. It is apparent, then, that the container 12 and lid 1%: provide a full encasement for the core 14D and its cushioning material 13. The folding over of ends 13 may effectively seal the encasement; however, a sealing material (not shown) may be used in conjunction With the lid 16 and the folded ends 18 to provide a more perfect seal if desired. Therefore, it is evident that any windings placed about the encasement may be vacuum impregnated without any deleterious effect upon the magnetic core 1d.

The magnetic core it is preferably a tape Wound core of an alloy made in accordance with the patent to E. A. Gaugler, 2,569,468, issued October 2, 1951. The invention, however, is not limited by the type core within the container 12, the principles of this invention being applicable as well to stacked washer cores, bobbin cores, powdered iron cores, and the like.

Preferably, container 12 is constructed of aluminum to reduce manufacturing costs and provide lightness in weight. However, other non-magnetic, comparatively strong, metallic materialsmeta'ls or alloys-may be utilized in constructing the container 12. For example, magnesium, brass, copper, and the like, are suitable materials for container 12.

Continuing to refer to FlGURES 1 and 2, the lid 16, which, as hereinbefore mentioned, prevents eddy current from being induced in, and from circulating around, the container 12 since the electrical current path is broken thereby, may be made of any electrical insulating material which has the desirable strength and temperature characteristic for .a given situation. For temperatures near 500 F., silicone resin impregnated glass or a polymer of tetrailuoroethylene as manufactured under the trade mark Teflon or other suitable materials may be used. Alternatively, the lid 16 may be made of a nonmagnetic metal such as aluminum and insulated (for example, with a polymer of trifiuorochloroethylene as manufactured under the trade mark Kelat least along one of its marginal edges Where contact would otherwise be made with the container 12. For lower temperatures, thermosetting plastics such as phenolic resins (e.g., phenol formaldehyde and phenol furfuraldehyde resins) or a melamine formaldehyde resin may be employed as the ,1 FLU- material for the lid. Any other electrical insulating mama netic core m9. *{owever such cushionin material will be absorbed to some extent by lid 16 and, particularly, by lids made of the above-mentioned thermosctting plastics.

3 ill stratcs a method of obviating the use s cushioning material. Around the bottom closed end of the container 12 are placed The specific it will be apparent, how- 'i enclosure is completely filled with silisubsequent curing of the rubber will -..d to cause a pressure within the container which may After ore 1%, as shown in FZGURE 4, another antities of silicone rubber may be around the then exposed end of the core. inc efo-e, after the insertion of lid 16, the folding over of end portionand the apnlication of a silicone varnish on the out e of the encasement, both the silicone b may be cured simulc which will not adversely affect tics of the core 19. The ma is consequently prevented from movement, particularly n the idewise direction.

Anotwr nodii tion is shown in 5 and 6 wherein not only the discrete quantities 221i and are utilized, but also .ition'tl discrete quantities 2d of silicone rubber are ed along the inner sides of container at desirable spacings. The core 119 is then cushioned permanently to prev nt movement thereof against any part of the contain 12 or the lid 16.

Modifications of this ii. ention not described herein will become apparent to those skill d in the art. Therefore, it is intended that the matter contained in the foregoing description and the accompanying drawings be interpreted as illustrative and limitative, the scope of the invention being defined in the appended claims.

What is claimed is:

1. Method for assembling a magnetic core device having a magnetic core -upported within an encasement which includes a trougl e metallic non-magnetic container having an or en end and a nonmagnetic closure means for the open end of the container comprising the steps of inserting a magnetic core within the trough-like nonmagnetic metaliic container,

distributing a cushioning material Within the container,

disposing an electrically insulatin closure in the open end of the container, and

deforming the container to secure the closure means to the container.

2. A method a in claim 1 further including the step of a plying electrical insulating mater around the outside of at least a portion of the metal container.

3. Method for assembling a magnetic core device having a magnetic core cushioned within an encasement which includes a trough-like metallic non-magnetic con tainer having an open end and electrically insulating nonmagnetic closure mcans for closing the open end of the container comprising the step of inserting a magnetic core into the trough-like metallic container,

injecting a cushioning material into the container,

placing the electrically insulating closure means in the open end of the container,

joining the container and the closure means by deformportions of the container, and

applying electrical insulating material to an exterior surface of the container.

Method for assembling a ma netic core device having a magnetic core supported Within an encasement which the magnetic c nctic core i includes a trough-like metallic, non-magnetic container having an open end and a non-magnetic closure means for the open end of the container comprising the steps of distributing a cushioning material Within the container, inserting a magnetic core into the container in contact With the cushioning material and spaced from the container by the cushioning material,

applying electrical insulating sealing material to the closure means, placing the closure means in the open end of the container with the sealing material separating adjacent surfaces of the container and the closure means, and

joining the container and closure means by deforming portions of the container.

5. Method for assembling a magnetic core device having a magnetic core supported in cushioning material Within an encasement which includes a trough-like metallic non-magnetic container having an annular open end and non-metallic non-magnetic closure means for closing the annular open end of the container comprising the steps of placing a magnetic core in the container,

distributing cushioning material Within the container,

curing the cushioning material,

placing the closure means in the open end of the container,

joining the container and closure means by deforming portions of the container, and

applying an electrical insulating material to an exterior surface of the container.

6. Method for enclosing a toroidal magnetic core in which the core is supported in cushioning material Within an encasement to prevent mechanical vibration from being transmitted to the core, the encasement including an annular trough-like metallic non-magnetic container for partially enclosing the core and non-magnetic electrically insulating closure means for completing enclosure of the core, With the container having end portions defining an annular opening and having a circumferential ledge at the opening of the container for supporting the closure means, comprising the steps of inserting a magnetic core into the container,

injecting cushioning material into the container,

disposing the electrically insulating closure means in the annular opening of the container so as to be supported by the circumferential ledge, and

securing the closure means to the container by moving end portions of the container into contact with the closure means.

7. The method of claim 6 further including the step of applying an electrical insulating material to an exterior portion of the container.

8. Method for enclosing a toroidal magnetic core in Which the core is supported in cushioning material within an encasement to prevent mechanical vibration from being transmitted to the core, the encasement including an annular trough-like metallic non-magnetic container for partially enclosing the core and non-magnetic electrically insulating closure means for completing enclosure of the core, With the container having end portions defining an annular opening and having a circumferential ledge formed at the opening of the container for supporting the closure means, comprising the steps of placing cushioning material within the container,

placing a magnetic core in the container in contact with the cushioning material and spaced from the container by the cushioning material,

placing the electrically insulating closure means in the annular opening of the container so as to be supported by the circumferential ledge, and

joining the container and closure means by folding over end portions of the container.

9. The method of claim 3 further including the steps of applying electrical insulating material to at least a portion of the exterior of the container.

References Cited by the Examiner UNITED STATES PATENTS 2,608,610 8/52 Thulin 29-15556 2,743,308 4/56 Bardsley 336-96 2,909,741 10/59 Arntzen et al. 336-219 WHITMORE A. WILTZ, Primary Examiner.

JOHN F. CAMPBELL, Examiner. 

1. METHOD FOR ASSEMBLING A MAGNETIC CORE DEVICE HAVING A MAGNETIC CORE SUPPORTED WITHIN AN ENCASEMENT WHICH INCLUDES A TROUGH-LIKE METALLIC NON-MAGNETIC CONTAINER HAVING AN OPEN END AND A NON-MAGNETIC CLOSURE MEANS FOR THE OPEN END OF THE CONTAINER COMPRISING THE STEPS OF INSERTING A MAGNETIC CORE WITHIN THE TROUGH-LIKE NONMAGNETIC METALLIC CONTAINER, DISTRIBUTING A CUSHIONING MATERIAL WITHIN THE CONTAINER, DISPOSING AN ELECTRICALLY INSULATING CLOSURE IN THE OPEN END OF THE CONTAINER, AND DEFORMING THE CONTAINER TO SECURE THE CLOSURE MEANS TO THE CONTAINER. 